Improved drilling mud and method of use



Unite States Paten 2,8053% Patented Sept. 10, 1957 IMPROVED DRILLING MUD AND METHOD OF USE No Drawing. Application December 22, 1952, Serial N0. 327,408

Claims. (Cl. 252--8.5)

This invention relates to an improved drilling fluid. In one specific aspect, it relates to an improved drilling mud having a reduced fluid loss. In another aspect, it relates to a drilling mud having improved rheological properties.

In the art of drilling wells, especially drilling by the rotary method, it is necessary to use a drilling mud, as is well understood in the art. The drilling mud performs many functions necessary to successful completion of the well being drilled. The drilling mud, in addition to performing other functions, lubricates the drill stem, car-- ries the cuttings to the surface of the well, and forms a filter cake on the walls of the well preventing loss of at least any substantial amount of water from the drilling mud to the natural formations in the well. The weight of the mud prevents blowouts of formation pressures especially when weighting agents are employed. In order to perform these important functions properly, the drilling mud must have suitable viscosity and other qualities at all times in spite of adverse conditions encountered in drilling the well. Thixotropic properties of the mud support the cuttings during any time the pumps are shut down.

In drilling wells there are two major difficulties caused by natural formations penetrated. The first of these difficulties is that if salts such as sodium chloride or calcium sulfate are encountered the salt will cut ordinary driiling mud so that its viscosity is entirely too high, the clay particles are flocculated, and there is grave danger of the drilling pipe twisting in half or gas cutting or a blowout occurring due to the salt cutting of the mud. The other difficulty encountered is that when a formation known as heaving shale is penetrated, this heaving shale absorbs water from the drilling mud and by a caving or disintegration action common to bentonite materials, the well hole is closed around the drill string choking off the circulation of drilling mud and often seizing the drill string so that the drill string twists in half.

The aspects of this invention are attained by the following objects.

It is an object of this invention to provide a drilling mud having reduced water loss characteristics.

It is another object to provide a drilling mud whose viscosity and gel strength are maintained at a desired low level.

It is another object to provide a method for drilling an oil well bore through various formations without deleterious effect upon the chilling mud used.

It is still another object to provide an improved drilling mud that is resistant to the action of calcium sulfate and sodium chloride.

Other objects and advantages will be apparent to one skilled in the art upon reading the disclosure of this invention.

I have discovered that a latex can be incorporated into a drilling fluid and that the fluid loss characteristics of the drilling fluid are thereby substantially enhanced. Both natural rubber and synthetic rubber latices can be em ploycd in the practice of my invention.

'l Latices gf synthetic rubberwhich are applicable to the practice of my invention include polymers of conjugated dienes containing 4 to 6 carbon atoms per molecule, including styrene, 1-3 butadiene, ichloroprene, isoprene, methyl pentadiene, 2-3 dimethyl 1-3 butadiene, alpha methyl styrene and halogenated styrenes. The polymers can be homopolymers or copolymers including terpo1y mers.

The latex can be stripped of any unpolymerized monomer after the polymerization is terminated or can be used as prepared. Monomers which remain in the latex exert no deleterious effect upon the drilling mud.

The latex, when prepared will usually contain from 20 to 30 weight percent of solids as dispersed rubber. The solids content, however, can be varied over wide limits according to the dilution requirements of the mud and can contain from 1 to weight percent of solids. Latices can be prepared containing 90 weight percent solids and such concentrated latices are desirable for economy of transportation. The concentrated latex can be diluted to any desired solids content before being added to the drilling mud.

The pH of the latex is controlled by the emulsifier used and since most drilling muds are alkaline it is desirable to use an alkaline emulsifier in preparing the latex so as to avoid coagulation of the latex in the drilling mud.

The latices are prepared by conventional methods and can be added with the makeup water in the form of a low solid. content latex or a more concentrated latex can be employed if dilution of the drilling mud is undesirable. The latex is compatible with a water base drilling mud and such drilling muds having latices incorporated therein have been found to be resistant to the action of calcium sulfate and sodium chloride.

In drilling a well with rotary tools, it is the usual practice to continually add water to make up for that which is lost to the formations through which the bore hole penetrates and to increase the volume or body of drilling mud as the well bore progresses downwardly. Finely ground materials resulting from the action of the bit are suspended in this additional water so as to create a continually enlarged volume of drilling mud.

It is both convenient and desirable to add this additional water in the form of a latex, which is low in solids, for example, one which contains from 1 to 50 weight percent solids, so as to maintain the concentration of latex in the body of drilling mud constant or to gradually increase the amount of latex in the body of drilling mud.

The following examples demonstrate the improvement of a water base drilling mud effected by the practice of this invention.

TESTS The tests of the properties of the drilling muds were all made with standard drilling mud laboratory equipment employed in standard procedures.

The measurements of pH were all made with aBeckman Laboratory Model G pH meter. The viscosity measurements were all made with a Stormer viscosimeter 1931 model made by Arthur H. Thomas Company. The mixing of samples was always for 30 minutes with a Hamilton Beach No. 33 high speed mixer. Sodium chloride and calcium sulfate content was controlled by adding weighed amounts. The filter cake thickness and water losses were all determined with an A. P. I. low pressure wall building tester filter press with a pressure of lbs. per square inch applied for 30 minutes. All temperatures were approximately room temperature. All barrels are 42 U. S. gallon barrels.

MATERIALS The 6 percentbentonite mud used in these tests was prepared by mixing 6 weight percent of, Wyoming ben-.

. 4 toniteindistilled water. The mixture was passed through Table V a colloid mill so as to thoroughly disperse the bentonite. V

The polybutadienelatex used in the examples was pre- Composition of Mud, Added l tb l pared using thefollowmg recipe. 5 Y 7 Vis. xi /g5 L985, Table I 6% bentolatex water quebra- NaOH OaSOl 0p 7 Parts by weight nite cho Water 180.00 1 V V Butadiene 100.00 0 100 0 0 Sodiumalkyl toluene sulfate 1.500 10 28 58 1} 8 V 8 8 g g}; Diisopropylbenzenehydroperoxide 0.097 g8 8 g l g. 8% 8 q; 3:8. l ,I i -0 50' 0 50 110 05. 1.0 4' 19f01 FeSo4-7H2O 0.140 I Y Mercaptanblend 0.500 The amount of latex added will bedetermmed by the Booster added after 2.5 hours; V V fluid loss requirements of'the drilling mud and the solids H20. p 5.000 content of added latex will be determined by the demand Diisopropylbenzene hydroperoxide 0.049 'for water on the part of the drilling mud. The amount .K4P2O7 0.088 of latex added in terms of total solid andexpressed 'as FeSO4-7H2O 0.070 20 pounds per barrel of drilling mud will vary-over wide.

- A o. 4 ranges and can be from 5 to 75 pounds per barrel ggiiggg "f" although both smaller and larger amounts-are'contem Noon-e gg plated in the practice of this invention us ally the amo nt 1 Y 0 Y of solids will be in'the order of 10 to 60 pounds per gg gfggfag "T -"T" 2 Wei ht green; 25 barrel, preferably to 60'pounds per barrel. V

p 1' "7" p Although the examples in this case are directed to i hl gng feri gg ggk z/ 5 8 1 allphatlc melclwtans the treatment f a water base drilling nud, the latices p p of this lnventlon can also be incorporated 1n emuls1on--, latex was a accqrdmg to the type drilling muds and inoil-base drilling muds The following W b 30 more concentrated latices having solids contents in the Ta le H order of 80 to. 90 weight percent of the latexare pre l V Parts by welght ferred for use in an oil-base drilling mud in order to' .'-'1---' '"-'f- 180000 avoid cutting the oil with'added water; When. used with 4 f ""j f 'f 7 emulsion-type drilling muds, the water in the latex Will styrene. 3- act to dilute the Water phase of an ,oil-in-water emulsion Alkyl aryl sodlum sulfonate (1750 or Willbe dispersed in awater-in-oil emulsion. Thus, 'Tert-butyllsopropylbenzene hydroperoxldeihn 0-114 .the solids content of the latex usedin an emulsion-type Q (1040 drilling mud will be determined by the Water require- T* ments of the drilling mud treated. 5 FeSO47HVEO 0440 40 Variations and modifications are possible 'within the, Mercaptan blend V V scope of the disclosure of this invention', the essence of A blend of tertiary C12,'C14- and C10 aliphatic mercaptans Which is that latices have been found to be excellent in a ratio of 3 1 1 parts by Weight. drilling u additivea i f The results of tests conductedupon bentonite base drill- I lai v y 1 f 1 V H g mud p po t i s qo y latex are 1. In a process for, drilling a Well WithQWel-l drilling tabulated 1n Table III. The addition of the latex 0 th too-ls wherein there is circulated in the Well a Waterbase 6 percent bentonite results in dllutlon of the mud theredrilling mud containing colloidal particles of'clayey lnate fore the results are compared. to those of a diluted rial suspended insufficient Water to render the saine'cirbentonite mud. 'culatable, the rneth'odof forming a'filter cake; on the Table 111- Composition of Mud, Percent Added to mud, lb/bbl. by volume Visc., Gels, g., Water-l0ss,; V V cps. 0-10min. ILL/30min. 6% bentonite latex water" Queb. NaOH 011804 NaOl 0 100 0 1.0 1.0 0 0 2.5 0-0 .1012 0 50 0 0 0 0 3.0 0-0 19.5 50 V 50' 0 0 0' 0 .0 8 0-0 7.0 50 0 50: 0 0 0 V 2 10 5-10 19.0' 50 14 36 0 o 0 2 12 5-5 13.5 50 29 21, 0 0 0 2 16 5-8 10.0 50 43 7 0 0 0 2 1 1s 5-8- 6 5 50 0 v 50 1.0 0.5 0 0 3 0-0 17.0 50 50 0 1.0 .0.5 $0 0 -5 0-2 7.5 50. 50. 1.0 0.5. 0.5 0 3.5 0-0 15.5 50 50 0 1.0 0.5 0.5 0 7.0. 0-0 6.0 .50 0 50 1.0 0. 5 1.0 0 4 o-5 19.0 1 50 l. .50 0 1.0 0.5 1.0 0 10 0-10 7.2 50 0 50 1.0 0.5 3.0 0 14 10-40 36 50- 1 50 1.0 0.5 3.0 o 62 20-35 14 50 0 50 1.0 0.5 .0 .1 2 0-0 16 .50 50 1.0 0.5 0 -1 5 0-0 7.0 50 0 50 -1.0 0:5 0 y 2 3 0-0 16 50- 50. 0 1.0- 0.5 0 2 17 0-1 7.0 50 0 50 .110 0.5 0 4v 6 0-2 16 50 v 50 0 1 .0 0.5 0 -4 10, 0-3, 65 The results of tests conducted upon bentonite base 7 Wall of said Well so as'todecr ea se' thel oss offluid from drlllln'g -muds-treatediwith a: butadiene-styrene latex are 7 said drilling m'udcontained the'rgein into surrounding' iearth-e .forinations.jwlriehf'comprises admixingwith said j drilling mud a rubber latex in an amount and a total solids concentration sufiicient so as to lower the fluid loss through said filter cake and to maintain the viscosity of said drilling mud within desired limits and contacting said wall of said Well with the resulting drilling mud so as to form said filter cake thereon.

2. The process of claim 1 wherein said latex is a natural rubber latex.

3. The process of claim 1 wherein said latex is a synthetic rubber latex.

4. A water base drilling mud comprising in combination sufiicient water to maintain the mud as a fluid; sufficient bentonitic clay to form a filter cake on the wall of the well; about 1 /2 to 2 pounds of a mixture of sodium hydroxide and quebracho per barrel of drilling mud; and from 5 to 75 pounds of rubber, as a latex, per barrel of drilling mud.

5. The drilling mud composition of claim 4 wherein the latex is a natural rubber latex.

6. The drilling mud composition of claim 4 wherein the latex is a synthetic rubber latex.

7. In a process for drilling a well with well drilling tools wherein there is circulated in the well a water-base drilling mud containing colloidal particles of clayey material suspended in sufiicient water to render the same circulatable, the method of forming a filter cake on the wall of said well so as to decrease the loss of fluid from said drilling mud contained therein into surrounding earthen formations which comprises continually adding to said circulating mud a rubber latex so as to maintain the amount of rubber in the drilling mud in the range of 5 to 75 pounds of rubber per barrel of drilling mud; and circulating said drilling mud.

8. The process of claim 7 wherein the latex is a polybutadiene latex containing from 1 to weight percent of dispersed solids.

9. The process of claim 7 wherein the latex is a butadiene-styrene latex containing from 1 to 50 Weight percent of dispersed solids.

10. A water base drilling mud comprising a suspension of about 6 weight percent of clayey material in water; about 2 pounds per barrel of drilling mud of a mixture of sodium hydroxide and quebracho; and from 5 to pounds per barrel of drilling mud of rubber as a latex.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,927 Van Campen Oct. 15, 1940 2,342,588 Larkin Feb. 22, 1944 2,380,156 Dobson July 10, 1945 2,481,339 Penfield Sept. 6, 1949 2,502,191 Williams Mar. 28, 1950 2,537,114 Young et al. Jan. 9, 1951 2,612,485 Baer Sept. 30, 1952 2,623,851 Salathiel Dec. 30, 1952 2,697,071 Kennedy et al. Dec. 14, 1954 2,743,233 Fisher Apr. 24, 1956 OTHER REFERENCES Bowie-Hardening of Mud Sheaths, Bureau of Mines Report of Investigations No. 3354, Nov. 1937, pages 7, 8, 9, 13, 15 and 17. 

1. IN A PROCESS FOR DRILLING A WELL WITH WELL DRILLING TOOLS WHEREIN THERE IS CIRCULATED IN THE WELL A WATER BASE DRILLING MUD CONTAINING COLLOIDAL PARTICLES OF CLAYEY MATERIAL SUSPENDED IN SUFFICIENT WATER TO RENDER THE SAME CIRCULATABLE, THE METHOD OF FORMING A FILTER CAKE ON THE WALL OF SAID WELL SO AS TO DECREASE THE LOSS OF FLUID FROM SAID DRILLING MUD CONTAINED THEREIN INTO SURROUNDING EARTHEN FORMATIONS WHICH COMPRISES ADMIXING WITH SAID DRILLING MUD A RUBBER LATEX IN AN AMOUNT AND A TOTAL SOLIDS CONCENTRATION SUFFICIENT SO AS TO LOWER THE FLUID LOSS THROUGH SAID FILTER CAKE AND TO MAINTAIN THE VISCOSITY OF SAID DRILLING MUD WITHIN DESIRED LIMITS AND CONTACTING SAID WALL OF SAID WELL WITH THE RESULTING DRILLING MUD SO AS TO FORM SAID FILTER CAKE THEREON. 